Metamizol: Formula, Presentation, Indications, Mechanism of Action, Dosage, Side Effects and Interactions

It is a drug or a non-steroidal compound with potent analgesic, antipyretic and spasmolytic properties.

Its use has been banned in some countries, while in other countries, its use has been restricted for some pathologies.

Chemical formula

  • Its active ingredient is sodium and magnesium metamizole.
  • C13H16N3O4SNa.


The Metamizole has the following presentations:

In tablets:

Whose active ingredient is sodium metamizole, and the other components of the formula are sodium bicarbonate, talc, corn starch, lactose, and magnesium stearate?

In capsules:

It also has magnesium metamizole as an active ingredient, and the other components are titanium dioxide, magnesium stearate, erythrosine, indigotin, and gelatin.

In envelopes:

Each sachet has 1 or 2 gr of magnesium metamizole, and the other components are mannitol, sodium saccharin, povidone K29 / 32, orange flavor, and coloring.

In blisters:

Magnesium metamizole with distilled water. Some blister presentations contain metamizole sodium.


In suppositories:

The active substance is magnesium metamizole. Each suppository contains 500 or 1000 mg of magnesium metamizole. Triglycerides of fatty acids accompanied her.


This medication is used to treat acute postoperative or post-traumatic pain, colic pain, and pain of tumor origin.

It is also used in cases of high fevers that do not respond to treatment with other antipyretics.

Mechanism of action

The mechanism of action is based on the inhibition of central cyclooxygenase-3 and the activation of the cannabinoid system.


Dosage in cases of renal or hepatic insufficiency:

In patients with renal failure and liver function, geriatric patients, and debilitated patients, the administration of high doses should be avoided.

In adults and adolescents over 15 years of age:

  • The recommended dose in capsules and tablets is 500 mg, 3 to 4 times a day.
  • The maximum daily amount is 4000 mg per day.
  • After 30 to 60 minutes of oral administration of the drug, the therapeutic effect can be expected.
  • In envelopes, a single dose of 1 to 2 gr of magnesium metamizole is recommended every 8 hours, without exceeding 6 g per day.
  • A period of 8 hours should be left between each dose.
  • In ampoules, administer one every 12 to 24 hours intravenously deep and slowly or intramuscularly.
  • If the patient has cancer and presents a lot of pain, it can be administered up to 6 grams daily, divided into three administrations.

Side effects

Metamizole rarely causes allergic reactions and, in sporadic cases, can be very serious and endanger the patient’s life.

These allergic processes can appear, even if Metamizole has been used previously, without any reaction.

Generally, these side effects occur within one hour after administering the medication.

Mild allergic reactions usually manifest as symptoms of the skin and mucous membranes, such as:

Itching, burning, redness, hives, swelling of the skin, and respiratory difficulties, less frequently, cause gastrointestinal discomfort.

This type of mild reaction can progress and become severe forms with the presence of generalized urticaria, swelling in the feet, hands, lips, throat, and respiratory tract ( angioedema ).

It can also cause severe bronchospasm, altered heart rate, and decreased blood pressure that can sometimes be preceded by an increase in blood pressure and circulatory shock.

In patients with asthma induced by analgesics, intolerance reactions usually manifest as severe asthma attacks.

Reactions such as a decrease in blood pressure may occur.

Rarely do these reactions to the medication cause a decrease in the white blood cell count ( leukopenia ) and, more rarely, in the platelet count in the blood ( thrombocytopenia ).

In these cases, inflammatory lesions may occur in the mucous membranes and sore throats, and the patient may develop a fever.

Warnings and contraindications

Metamizole is contraindicated under the following conditions:

In cases of glucose-6-phosphate dehydrogenase deficiency, severe hepatic failure, severe renal insufficiency and acute intermittent porphyria.

It is also contraindicated during pregnancy and in patients under 18.

It should be used with caution in patients with low blood pressure or unstable circulation since Metamizole can cause hypotension.

Metamizole is contraindicated in hypersensitivity to the component or to other substances derived from pyrazolones or other parts of the formula or if it is intolerant to dyes, preservatives, or alcohol.

If the patient has suffered from symptoms such as asthma, rhinitis, or urticaria, after administering acetylsalicylic acid, paracetamol or non-steroidal anti-inflammatory drugs, its administration is contraindicated since a cross-sensitivity may occur.

Among the most common allergy symptoms to the medicine can include:

  • The presentation of asthma attacks with breathing difficulties, audible wheezing or rapid breathing, and the appearance of edema or swelling more or less sudden on the face.
  • They can appear on the lips, tongue, or another part of the body, but this symptom is especially critical if it affects the vocal cords.
  • They can also appear as hives, itching, and rash, and in severe cases, the occurrence of an anaphylactic shock with loss of consciousness, pallor, and excessive sweating.

Metamizole is also contraindicated in cases where the patient has suffered from a decrease in the number of white blood cells or agranulocytosis after having used this drug at other times.

And special care must be taken when the medication is administered for the first time, and with this administration, the patient begins to present signs or symptoms such as:

  1. Red spots on the skin of sudden onset of very high fever.
  2. Shaking chills.
  3. The patient has pain in the mouth, nose, or throat.
  4. There are sores in the mouth, vagina, penis, or anus resulting from decreased white blood cells.

In these cases, it is necessary to stop the treatment immediately and consult the doctor.

In those cases where the patient has previously suffered a bone marrow function disorder, for example, after chemotherapy or if he suffers from blood diseases, Metamizole is contraindicated.

Its use is contraindicated in conjunction with the ingestion of alcohol since taking Metamizole together with alcohol can enhance the effects of both and cause severe consequences in the patient.

There are special physiological situations, such as pregnancy and lactation, children and adolescents, where the administration of this medicine should only be done when the doctor has evaluated the benefit-risk ratio.

In cases of pregnancy, it is advisable not to administer the medication either in the first or in the last trimester of pregnancy.

The metabolites of Metamizole pass into breast milk, and it is for this reason that administration of the same should be avoided for 48 hours after the Metamizole is administered.

Metamizole should only be administered under strict medical supervision when it comes to children and adolescents.

It is not recommended to use Metamizole in children under three months of age or even in those weighing less than 5 kg.

If partial doses of the drug presentations are necessary, it is recommended to use only the specialties that can be divided with precision.

In the case of driving cars and using machines or equipment that require a state of alert, it is not recommended to perform these activities if you are taking the medication in high doses.


The doctor must be informed of their use when using other medicines, even if he has recently used herbal products.

In these cases, it may be necessary to change the dose, in some cases, suspend a treatment.

This applies to all types of drugs, but especially in the administration of medications such as:

  • Anticoagulants such as warfarin, acenocoumarol, heparin, and others.
  • Antibiotics, such as penicillin and sulfonamides.
  • Corticosteroids
  • The medicines used to treat diabetes.
  • Antiplatelet drugs such as Clopidogrel.
  • Antihypertensive medications such as angiotensin-converting enzyme inhibitors and diuretics.

Among the drugs that can increase the levels of Metamizole in the blood and cause adverse effects, we have sedatives and hypnotics.